1990 Mustang 5.0 won't accerate past 3,000 RPMs

[DSGB302]

I have a 1990 5.0 with a powerdyne supercharger (currently discontinued) and I when I accerate hard it hessitates or bucks at around 3,000 RPMs know matter what the boost controller is set to or timing. I have a Walbro 255 lph fuel pump, vortec FMU, MSD boost controller, and Kirban adjustable fuel pressure regulator. Engine is stock minus Ford Racing shorty headers, 2.5 full exhaust X Pipe with flowmaster 40s. At first I though maybe its due to the 15lb. pulley but then I tried with the belt off the supercharger/ Just to see if it was getting too much air for the stock MAF and and injectors no change. I tried with and without the FMU and at every adjustable psi I could think of with the Kirban fuel pressure regulator and am now out of ideas. I plan to get 30lb injectors and a 73mm MAF with 30lb sampling tube but I've know of other mustangs the can run with stock injectors but I am out of options please hook me up with some input. Thanks all

 

[LaserSVT]

15 lbs on a stock internaled block? Thats insaine! I wonder if you bent some pushrods.

Oh well, check your plugs and wires. See if a wire is arcing out or mabey a plug or two is fouled/burnt. Also look at the power wires to the coil and/or ignition box.
If thats all good then you may have some bent valves from runing 15+ psi

Stupid question, do you have the resistor pulled? I actually know someone who forgot to put it back in after seting his timing and on his first run was boging hard after 3200 or so. Took him 5 hours to find the problem

 

[DSGB302]

15 lbs on a stock internaled block? Thats insaine! I wonder if you bent some pushrods.

Oh well, check your plugs and wires. See if a wire is arcing out or mabey a plug or two is fouled/burnt. Also look at the power wires to the coil and/or ignition box.
If thats all good then you may have some bent valves from runing 15+ psi

Stupid question, do you have the resistor pulled? I actually know someone who forgot to put it back in after seting his timing and on his first run was boging hard after 3200 or so. Took him 5 hours to find the problem

Plugs and plug wires are new so not burnt or shorted I plan on putting the 9# pully on when I get the belt that fits it but the 15# was on when I got it. I also tried running without the belt so it wouldn't blow too much extra air just to see if it would run right no luck though. while accelerating at idle and it doesn't seem like the rods are bent even though I know its not hard to bend them with over reving and boost I did that on a 347 I had once. Oh and the resistor is on I've played with the timing plenty trying to see if I just needed to find a sweet spot.

 

[BlownFiveLiter]

What's your spark plug gap set at? It sounds like you're blowing out your spark to me. Try a gap of .035 if you haven't already. And 15lbs from a powerdyne? I bet you'll see closer to 10...

 

[93 LX]

any codes?

 

[DSGB302]

I have my gap set a .32 I've tried autolite 25s and 24s. I am aware powerdyne isn't as great as vortech and so forth its preety old. I don't have any codes that stand out 41, 91, 13 I think they were. I once had a 89 but its been gone since the last time I cleared it.

 

[90lxcoupe]

im gonna guess its one of the two modules on the distributor.

Also, ditch that FMU, get some 42lb injectors and a custom tune

 

[DSGB302]

im gonna guess its one of the two modules on the distributor.

Also, ditch that FMU, get some 42lb injectors and a custom tune

Just changed the EFI module no luck still. I do have 30lb injectors on the way and a 30 maf. I am alil confused about when I took the belt off the super charger pulley to simulate stock form it still wouldn't accel past 3 grand.

 

[90lxcoupe]

Just changed the EFI module no luck still. I do have 30lb injectors on the way and a 30 maf. I am alil confused about when I took the belt off the super charger pulley to simulate stock form it still wouldn't accel past 3 grand.

its got nothing to do with the blower... Did you replace the module inside the dist, or the TFI one on the outside...

I had a similar problem a while ago, and it was the module inside the dist under the cap.

 

[DSGB302]

its got nothing to do with the blower... Did you replace the module inside the dist, or the TFI one on the outside...

I had a similar problem a while ago, and it was the module inside the dist under the cap.

I changed both it looked like it still had the same OE distributor so I changed the whole assy. and the module on the outside the new distributor comes with the inside module/pick up coil. I'm using an accel cap and rotor. That shouldn't matter should it?...

 

[BlownFiveLiter]

Do you know off hand what calibration your FMU is? You can do 4:1, 6:1, 8:1, 10:1, or 12:1, where your fuel pressure goes up X psi for each 1 lb of boost. IIRC, you should have a 12:1 calibration disc if you're still running 19 lb injectors.

 

[90lxcoupe]

To me it sounds like spark problems, was the car running good before? dont change to many things at once... just do one thing at a time, sometimes you fix 5 things at once and your chasing your tail and wasting alot of money

 

[Mustang5L5]

Just changed the EFI module no luck still. I do have 30lb injectors on the way and a 30 maf. I am alil confused about when I took the belt off the super charger pulley to simulate stock form it still wouldn't accel past 3 grand.

Forget the 30# calibrated MAF.

With your combo you should be going custom dyno tune...esp if you are running that much boost on a stock block.

 

[DSGB302]

Do you know off hand what calibration your FMU is? You can do 4:1, 6:1, 8:1, 10:1, or 12:1, where your fuel pressure goes up X psi for each 1 lb of boost. IIRC, you should have a 12:1 calibration disc if you're still running 19 lb injectors.

I am not sure but I also have a Kirban adjustable regulator and yesterday I bypassed the FMU and played with the fuel pressure regulator still same story.

 

[DSGB302]

Performance chips for superchargers

I ment to start a new post sorry.

 

[DSGB302]

Hey guys I put in some 30# injectors and now I have a beast that runs. Thanks for all the help and replys. I am also going to put a 9lb pulley back 15lb just feels like its gonna be too much for the car I used a friends 02 turbo eclispes to see how I match up and well at least one of us will be upping the boost.